<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<c:if test="${empty param.from}">
    <c:set var="cancelLink" value="list.html"/>
</c:if>
<c:if test="${not empty param.from}">
    <c:set var="cancelLink" value="${param.from}"/>
</c:if>
<a href="${cancelLink}">
    <img src="<%= request.getContextPath()%>/images/btn/functions1/btn_cancel.gif" class="btn"/>
</a>